A rabbit anti-human bladder cancer tissue antibody (RABCa) was prepared and was reacted against urine samples from a series of cancerous and non-cancerous patients by both micro-complement fixation and Ouchterlony gel diffusion. RABCa vs. urine from cancer patients showed a peak CV to 1 g of total protein vs. only 3 g with non-bladder cancer urines. When RABCa was reacted in agar gels against membrane antigenic extracts of bladder cancers and normal patients, a separate precipitation band of identity was visible against 66.7% of the cancer specimens (urines) and in only 3.2% of normal urines. Non-cancer bands could be removed by absorption with either normal bladder tissue or urine. Gel fractionation (Sephadex G-100 and G-200) of urines suggests that RABCa reacts in the CF and Ouchterlony assays with a component of urine which has a molecular weight greater than 100,000. A rabbit antisera to this active fraction has lead to the identification of both heat labile (70 degrees C - 30 min.) and heat stable cancer associated antigens. Further purification studies and assays have shown the heat labile fraction to be an immunoglobulin like molecule. Anti-immunoglobulin sera (IgG) in fact have shown precipitin bands in gel diffusion studies vs. 60% of cancer urines. The heat stable bands have been resolved into at least two components which can be separated by Sephadex G-100 chromatography. Studies in progress involve the production of an antiserum to the heat stable component and further identification of specific bladder cancer associated antigens. BIBLIOGRAPHIC REFERENCES: Monaco, A.P., Gozzo, J.J., Schlesinger, R.M. and Codish, S.D. Immunological detection of human bladder carcinoma. Annals of Surgery 182:325-333, 1975. Cronin, W., Gozzo, J., Codish, S., Gottschalk, Rita, Schlesinger, R. and Monaco, A.P. Immunological detection and partial purification of human urinary bladder tumor associated antigens (TAA) in urine. Fed. Proc. 34:1042, 1975 (Abstract).